Condition Monitoring of Horizontal Sieving Screens-A Case Study of Inertial Vibrator Bearing Failure in Calcium Carbonate Production Plant.

Predictive maintenance is increasingly popular in many branches, as well as in the mining industry; however, there is a lack of spectacular examples of its practice efficiency. Close collaboration between Omya Group and Wroclaw University of Science and Technology allowed investigation of the failure of the inertial vibrator's bearing. The signals of vibration are captured from the sieving screen just before bearing failure and right after repair, when it was visually inspected after replacement. The additional complication was introduced by the loss of stable attachment of the vibrator's shield, which produced great periodical excitation in each place of measurement on the machine. Such anomalies in the signals, in addition to falling pieces of material, made impossible the diagnostics by standard methods. However, the implementation of advanced signal processing techniques such as time-frequency diagrams, envelope spectrum, cyclic spectral coherence, orbits analysis, and phase space plots allowed to undermine defects (pitting on the inner ring). After repair, the amplitudes of vibration from the damaged bearing side were reduced by five times, while sound pressure was only two times lower. The quantitative parameters of vibrations showed significant changes: time series RMS (-68%) median energy of spectrograms (89%), frequencies ratio of cyclic spectral coherence (-85%), and average amplitude of harmonics in envelope spectrum (-80%). The orbits demonstrated changes in inclination angle (16%) and sizes (-48, … -96%), as well as phase space plots sizes (-28, … -67%). Directions of further research are considered.